Corona treatment is a method using an electrical corona discharge to modify a surface of a web to improve its ability to accept inks and adhesives. In a corona treatment, a high voltage electrode is mounted parallel to and spaced from a ground roller, which forms a grounded electrode. The air gap between the electrodes is energized, forming a corona, which, when web is passed therethrough modifies the material the web is formed of, and makes the web more receptive to ink and adhesives. Corona will be produced anywhere there is air within this air gap.
The web may have differing thicknesses, for example, if two pieces of the web are spliced together. As a result, the upper surface of the web at the splice will be closer to the high voltage electrode as it passes through the air gap. This may lead to undesirable results.
Currently, as the web is being passed through the air gap, the position of the electrode relative to the ground roller is manually adjusted. This is time consuming and can result in undesirable results.